III Russian-Spanish Congress

Meson gas properties and chiral symmetry restoration

10 Sept 2015, 16:40

20m

Santiago de Compostela

Session 10

Speaker

Angel Gomez Nicola (Universidad Complutense Madrid)

Description

I will discuss recent progress in low-energy QCD at finite temperature regarding chiral symmetry restoration and properties of meson gases relevant for Heavy-Ion Physics and lattice simulations. In particular, I will present a recent analysis of scalar and pseudo-scalar susceptibilities $\chi_S$ and $\chi_P^a$, which allows to understand chiral partner degeneration at chiral symmetry restoration in a consistent framework built from model-independent assumptions. On the one hand, correlator identities confirmed by Chiral Perturbation Theory allow to relate $\chi_P^a$ and quark condensates for different channels in the light and strange sectors. On the other hand, such identities and the $O(4)$ $S/P$ degeneration pattern are supported by direct analysis of lattice data for screening masses, quark condensates and scalar susceptibilities. The role played by the thermal $f_0(500)$ will be particularly emphasized. In fact, saturation of $\chi_S$ by the $f_0(500)$ state dynamically generated through thermal unitarization within ChPT, gives rise to a peak compatible with the lattice transition point, consistent with partner degeneration. I will also discuss resummation schemes such as large-$N_f$ in which properties such as thermal unitarity and the thermal $f0(500)$ pole behaviour hold exactly. Some recent progress on chiral symmetry properties in the presence of external magnetic fields could also be discussed.